Bulk Viscosity Of Liquid Research Articles

Объемная вязкость в жидкостях и в жидких дисперсных системах

The paper provides a brief review of studies of the bulk viscosity of liquids and liquid dispersed systems. Obtaining experimental data on the viscosity of liquid dispersed (colloidal) systems is complicated by a number of factors: the difficulty of creating monodisperse systems, various methodological problems of accurately measuring the size of particles, their concentration, degree of homogeneity, and distribution. And also the difficulty lies in the fact that with an increase in the concentration of particles, a liquid dispersed system from a Newtonian liquid becomes non-Newtonian. The absorption of acoustic waves in a liquid is associated with both shear and bulk viscosity. It is shown that in most cases the value of bulk viscosity is much higher than the value of shear viscosity, and their ratio changes with increasing temperature. The data obtained on the basis of the Stokes model of absorption of sound waves are considered.

Measurement procedure for acoustic absorption and bulk viscosity of liquids

A measurement procedure using a modified two-chamber pulse-echo experimental setup is presented, enabling acoustic absorption and bulk viscosity (volume viscosity) measurements in liquids up to high temperature and pressure. Acoustic absorption measurements are particularly challenging, since other dissipative effects, such as diffraction at the acoustic source and at acoustic reflectors, are typically superimposed to the measurement effect. Acoustic field simulations are performed, allowing to investigate acoustic wave propagation qualitatively. The absorption coefficient is determined by evaluating the signal spectrum’s raw moments and applying a method to identify and correct systematic measurement deviations. Measurement uncertainties are estimated by a Monte Carlo method. In order to validate the present measurement procedure, the acoustic absorption in liquid methanol, n-hexane, n-octane, and n-decane is determined experimentally and compared to literature data. The measurement results for methanol are additionally validated by comparison to bulk viscosity data sampled with molecular dynamics simulation.

Influence of liquid density variation on the bubble and gas dynamics of a single acoustic cavitation bubble

The effects of liquid density variation at the bubble surface on the dynamics of a single acoustic cavitation bubble are numerically studied. The Gilmore model together with a comprehensive hydrochemical model is used. The evaporation and condensation of water vapor are included in the hydrochemical model. The simulation results are compared to those resulting from the widely known Keller-Miksis model, which assumes a constant liquid density at the bubble surface. The numerical results for a single argon bubble in water reveal that the pressure and the temperature inside the bubble in collapse phase significantly increase, when the non-constant liquid density is used. These differences increase by raising the ultrasonic amplitude and by decreasing the bubble ambient radius and ultrasonic frequency. More importantly, at higher ultrasonic frequencies, the models give the same results regarding the cavitation dynamics and much more remarkably on the thermodynamic behavior of the bubble contents. Also, it is revealed that the entered number of water vapor molecules into the bubble in expansion phase through evaporation are less than the simulated one by the diffusion limited model. Notably, in the case of an argon bubble in aqueous solution of H2SO4(85wt%), a better match between the results of two models is observed. In addition, it is shown that considering the liquid bulk viscosity, arising from the rapid liquid density variation at the end of bubble collapse, in the Gilmore model leads to a slight growth in the collapse strength, temperature, and pressure within the bubble.

How important is the liquid bulk viscosity effect on the dynamics of a single cavitation bubble?

The influence of liquid bulk viscosity on the dynamics of a single cavitation bubble is numerically studied via Gilmore model with a new modified boundary condition at bubble interface. In order to more accurately describe the interior gas thermodynamics, a hydrochemical model is used. The numerical results for an argon bubble in water and aqueous H2SO4 show that including the liquid bulk viscosity slightly affects the bubble dynamics in collapse phase. This effect becomes significant only at high ultrasonic amplitudes and high viscosities. Moreover, the maximum pressure value inside the bubble is much more influenced than the maximum temperature. This finding lends support to results of Shen et al. [25] and significantly differ from some previous results reported in the literature.

Effects of bulk viscosity in non-linear bubble dynamics

The non-linear bubble dynamics equations in a compressible liquid have been modifiedby considering the effects of compressibility of both the liquid and the gas atthe bubble interface. A new bubble boundary equation has been derived, whichincludes a new term resulting from the liquid bulk viscosity effect. The influence ofthis term has been numerically investigated by considering the effects of watervapour and chemical reactions inside the bubble. The results clearly indicatethat the new term has an important damping role at the collapse, so that itsconsideration dramatically decreases the amplitude of the bubble rebounds after thecollapse. This damping feature is more remarkable for higher driving pressures.

Measurement of the bulk viscosity of liquid by Brillouin scattering.

The aim is to develop a rapid and direct method for measuring the bulk viscosity of a liquid as a function of temperature. Brillouin scattering of a laser beam in fresh water and salt water at different temperatures has been studied. The results show that there exists a close temperature-dependent relationship among the Brillouin frequency shift, the Brillouin linewidth, and the bulk viscosity of water. Thus the bulk viscosity of water can be determined directly from Brillouin-scattering measurements. The method has a high signal-to-noise ratio and high accuracy.

A surface laser-light scattering spectrometer with adjustable resolution

We describe a surface laser-light scattering (SLLS) spectrometer, which uses optical heterodyne detection to measure the temporal behavior of the thermally generated capillary waves at a fluid/fluid interface. From the measurement the interfacial tension and one of the bulk fluid viscosities are calculated. An instrument resolution model is described that characterizes the resolving power of the SLLS spectrometer based on the optical parameters measured at the photodetector. The instrument resolution is defined and measured, and the resolution is adjusted to optimize the signal-to-noise ratio. The model was verified using light-scattering measurements with wave numbers in the range 250–1750 cm−1 and with instrument resolution varied by more than a factor of 2. Measurements were made on several liquids whose viscosities vary over an order of magnitude. Data reduction used the analysis of thermally generated capillary waves recently published [A. Hajiloo and J. C. Slattery, J. Colloid Interface Sci. 112, 325 (1986)]. The values calculated for both surface tension and liquid bulk viscosity were in good agreement with the literature.

Bulk Viscosity of Liquids

The mechanisms for bulk viscosity are different between associated and nonassociated liquids. Here, a new mechanism for bulk viscosity is proposed from the standpoint of the hole theory of liquids and the rate process theory. This mechanism can explain the temperature and pressure dependencies of acoustic absorption for associated liquids and very viscous nonassociated liquids.

The Statistical Mechanical Theory of Transport Processes. VI. A Calculation of the Coefficients of Shear and Bulk Viscosity of Liquids

The theory of the coefficients of shear and bulk viscosity of liquids developed in the third article of this series is applied to the calculation of the coefficients of viscosity of liquid argon at its normal boiling point. The theory of the bulk viscosity, including a previously omitted term due to the rate of dilatation, is presented. With the use of the Lennard-Jones potential, a radial distribution function which is a much better approximation than the previously used one, and a new approximation to the friction constant, values are obtained for the coefficients of viscosity.

Errata: The Statistical Mechanical Theory of Transport Processes. III. The Coefficients of Shear and Bulk Viscosity of Liquids

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The Statistical Mechanical Theory of Transport Processes. III. The Coefficients of Shear and Bulk Viscosity of Liquids

A molecular theory of the coefficients of shear and bulk viscosity of monatomic liquids is developed on the basis of the general theory of transport processes presented in the first article of this series. With the use of the Lennard-Jones potential and a reasonable analytic approximation to the experimental radial distribution function, calculations of the coefficients of shear and bulk viscosity of liquid argon at 89°K have been carried out. The theory leads explicitly to ratios of the coefficients to the friction constant of the theory of Brownian motion. With a preliminary estimate of the friction constant, a value of the shear viscosity of liquid argon in moderately good agreement with experiment is obtained.